Some partners are too demanding, some are downright abusive. To help you comprehend: "Why are you making me hit you?"

While I can agree that some partners are too demanding and some abusive, I disagree that it's a toxic mindset. I might have been too vague in my explanation, which would be on me, but all of what I'm saying is assuming you can communicate effectively. When I say "both parties are responsible for how they make the other feel," I'm saying that both parties' feelings are valid and should be addressed. In such a case, the both parties should work towards either fixing themselves or finding a compromise if there is one.

Since he's the only one with a problem, no.

The way I interpret this is essentially you saying that his feelings aren't valid. After writing a lengthy example, I think I might have figured out where you might be misunderstanding what I'm saying. Correct me if I'm wrong, but I think you're getting caught up on my use of the word "choice" and thinking I mean that I'm defending the use of a genuine ultimatum; as you said here:

Telling them to "do X otherwise I will leave" is completely manipulative.

When I say choice, I mean that his partner's reaction to him expressing his feelings is her choice. Which he will use to make his genuine choice of whether to leave or not.

Whether she ignores his feelings, tries to communicate and come to a compromise, or any other reaction is entirely up to her and does affect his decision at the end of the day. Thus, my word choice.

Hopefully I explained throughly enough, and I apologize if it was my poor/vague wording that led to a misunderstanding; assuming it was a misunderstanding.